U.S. Pat. No. 6,706,406 discloses a ship hull design with hull plates formed from a pair of parallel ductile steel layers with an elastomer bonded to the steel layers in the space between the two layers. Voids may be provided in the elastomer, filled with rigid foam or light gauge steel. The elastomer arrests the development of cracks, which reduces hull damage during grounding or collisions.
When a ship is hit by an explosive projectile, the most noxious damage is due to the effect of explosion within the ship. The explosion leads to a pressure surge and high velocity fragments that can kill ship's personnel and create extensive damage to the ship's infrastructure.
One possible solution to the high velocity fragments problem is the use of armored bulkheads. Various technologies for manufacturing armored plates are known from the field of armored vehicles, such as use of hard grade steel, ceramics, fabrics of strong fibers or composites thereof. For example, an armor plate comprising a hard armor plate with an elastomer coating on the outside is known from an article titled “Elastomer-steel laminate armor”, by C. M. Roland et al., published in Composite structures, 92 pages 1059-1064. By coating the plate, a layer is formed that has no rigidity of its own, but is attached everywhere to the armor plate, so that it stretches everywhere together with the armor plate. The coating serves to increase penetration resistance. Roland et al note that the origin of blast and ballistic mitigation remains to be fully understood, but they mention energy absorption by rubber and strain delocalization Roland et al note that a multi laminate structure may be used, which can be extended to using multiple layers may be introduced into the coating. Roland et al give examples of very thin layers in the coating like 0.25 mm aluminum and 0.33 thick low modulus PU-1. With such an thin aluminum layer in the coating, the coating attaches the aluminum layer everywhere to the armor plate.
However, many of these technologies are unattractive for use in ships, in view of the vast number of plates required in ships, which leads to concerns about weight and costs. This further means that it is desirable that the protective plates as much as possible perform structural functions in the ship, which may conflict with the behavior of conventional armor. For example hard materials are often brittle, and hence vulnerable to pressure surge. Moreover, it may be difficult to weld armor plates to other structures in a way that the welds support a structural function in a reliable way.